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### Course: AP®︎/College Statistics>Unit 3

Lesson 3: Measuring variability in quantitative data

# Visually assessing standard deviation

Worked examples visually assessing the standard distribution.

## Want to join the conversation?

• so is this like the IQR or nah
• No, standard deviation is not the same as IQR.
• This is weird but I wanted to fully grasp what variance meant like I know it's SD squared and it shows the variability of the graph but I still don't know how it came to be. Please help me with that
• Think about it: remember how the standard deviation squared is the sum of all the points minus the mean squared? Since it is squared, there is no negative numbers, and only the distance from the mean matters on the value of the standard deviation. Therefore, if the distance between points and the mean is large, since it is squared, the standard deviation squared would be larger, and if the distance between points and the mean is small, the standard deviation squared would be smaller. After square rooting it, the standard deviation is still large or small based on the distance between the points.
• If the standard deviation is the typical distance from each of the data points to the mean, then what is the variance?
• The variance is the standard deviation squared.
• Would you call it standard deviation or sample deviation? When you can do it for the entire population then do you use them interchangably?